Mixing apparatus and method



1964 M. o. HOLOWATY ETAL 3,

MIXING APPARATUS AND METHOD Filed July 21, 1960 1 h, itnxjrierlifor ts A O. oowa 19 Aifa 11.60 m fein Cleo B. Sheets a, DM.LM2{ Hibbm aflvg United States Patent 3,151,844 MIXING APPARATUS AN D METHOD Michael 0. Holowaty, Gary, and Cleo 13. Sheets, Harnmond, Ind, and Harold A. Goldfein, Chicago, Iil.,

assignors to Inland Steel Company, Chicago, 111., a

corporation of Delaware Filed July 21, 19st), Ser. No. 44,462 13 Ciaims. (Cl. 259-45) The present invention relates generally to the mixing of tWo or more relatively finely divided materials, and more particularly to an improved method of mixing and apparatus for mixing a high-moisture content iron ore with blast furnace flue dust or for blending a low-grade iron ore concentrate into a mixture of high-grade iron ore.

In processing iron ore fines prior to agglomeration in a sintering operation, for example, it is desirable to pass the ore as taken from an ore stock pile through a screen of the required size to separate the larger particle size ore which doe not require sintering and to exclude foreign material from the sinter mixture. When the ore is dry or has a relatively low moisture content, such as when the moisture content is below 12% by weight, there is generally no particular difliculty in screening the ore. In certain wet climates and in certain wet seasons, however, considerable difliculty is encountered in screening wet ore which quite frequently has a consistency approaching that of mud. When ore of the latter consistency is encountered, usually it is the practice to avoid using the wet ore entirely until it dries. Where no ore other than the wet ore is available, the operator of the screening station can continue screening the wet ore by increasing the size of the openings in the screen. Enlarging the screen size, however, is usually undesirable because it requires the sintering plant to process a great deal of ore which actually does not require agglomeration. An alternative procedure is to mix the wet ore with suflicient hot, dry, blast furnace flue dust to permit effectively screening the resulting ore mixture.

The present technique of mixing wet ore with flue dust comprises discharging the wet ore into an ore pit of the screening station and adding the hot blast furnace flue dust thereto by means of a crane bucket and then mixing the materials by mean of the crane bucket until the operator considers the ore and flue dust thoroughly blended. The latter mixing method has several disadvantages. For example, the consistency of the resulting mixture is not uniform, the crane bucket is tied up for a prolonged period during the mixing operation, and a considerable amount of sensible heat in the hot fine dust is lost to the air, and thus is less effective in drying the wet ore.

It is, therefore, an object of the present invention to provide an improved method and apparatus for mixing two or more relatively finely divided materials.

It is a further object of the present invention to provide an improved method and apparatus for mixing and screening wet iron ore with hot, dry blast furnace flue dust to effect drying and mixing of the said ore.

Other objects of the present invention will be apparent from the detailed description and claims to follow.

It has been fouud that the foregoing and other objects of the present invention can be effectively and economically achieved by providing in the usual screening operation at a point between the supply source of two or more finely divided materials, preferably having a particle size less than about /2 inch, and the screening apparatu therefor, means for continuously supplying the said materials, such as wet iron ore along with hot, dry, flue dust, to the surface of a rapidly rotating mixing roll which propels the said materials at a relatively high rate of speed along a pathway generally transversely, and while the said mate- Fatented Get. 6, 1964 rials are moving at a high rate of speed abruptly stopping the movement of said materials by interposing a baffle plate in the pathway thereof. If desired, the materials are then allowed to fall or are guided onto a screen of the required mesh size, to effect the desired screening or separa tion of the ore.

The foregoing method and apparatus will be more clearly understood by referring to the following detailed description and claims when read in conjunction with the accompanying drawing wherein:

FIGURE 1 is a longitudinal vertical sectional view of apparatus comprising one specific embodiment of the pres ent invention taken along the line 1-1 of FIG. 2;

FIG. 2 is an end elevational view partially in vertical section of the apparatus of FIG. 1 with the baflie plates thereof removed; and

FIG. 3 is a vertical sectional view along the line 33 of FIG. 2.

In the specific embodiment of the present invention illustrated in the accompanying drawing, an iron ore stor age hopper 1t and a blast furnace flue dust storage hopper 11 each provided with adjustable gates 19a and 11a, respectively, are disposed above a continuous conveyor means, preferably in the form of an endless belt 12 passing over longitudinally spaced rolls 13, 14- fixedly secured on the shafts 15, 16, respectively, which are rotatably mounted in a frame 17 supported by the floor of the sinter plant so that the belt 12 can be moved in either longitudinal direction. Adjacent each end of the conveyor means disposed slightly outwardly of and below each of the rolls 13, 14, respectively, is a spiked mixing roll 18, 19, respectively. Each of the rolls 13, 19 is fixedly secured to a shaft 21, 22, respectively, which are rotatably mounted in the frame 17.

The conveyor belt 12 is preferably driven independently of the mixing rolls in order to provide the apparatus with the desired flexibility of operation. Thus, as shown in FIG. 2, the shaft 15 is operatively driven by means of a variable speed, reversible motor 24 through belt means 26 and a pulley or sprocket wheel 27 which is fixedly secured t0 shaft 15. The shaft 21 is connected through a sprocket wheel 28 and a sprocket drive chain 29 to a variable peed motor 39, capable of driving the said mixing roll 13 at the required rate of speed (e.g., -250 r.p.m.). The shaft 22 is connected through a sprocket wheel 28' and a drive chain 29' to a variable speed motor 39 which is capable of driving the mixing roll 19 at the required rate of speed (100-250 r.p.m.).

Mounted on the frame 17 and enclosing each of the ends of the conveyor means and mixing rolls 18, 19 is a baflie plate assembly 32, 33, respectively. Each said baflie plate assembly 32, 33 is comprised of spaced lateral side plates 34, 35 with connecting angularly disposed, upper end baflie plates 37, 37 and lower end baflie plates 38, 38, which are joined to each other and to the oppositely disposed side plates 34, 35, respectively. The upper baflle plates 37, 37 slope downwardly and outwardly in relatively close proximity to the opposite ends, respectively, of the conveyor belt 12 and to the upper surfaces of the mixing rolls 18, 19, respectively. The lower bafiie plates 38, 3S slope downwardly and inwardly from the lower edges of the upper baffle plates 37, 37 respectively, and are disposed adjacent the lower surfaces of the mixing rolls 18, 19, respectively. A vibrator 40 is secured to each of the upper baflle plates 37, 37' to insure against any buildup of material on the bathe plates. In the preferred form, the baflie plates 37, 37 and 38, 38 are movably mounted on the frame 17 to enable the said plates to be adjustable toward and away from the adjacent mixing roll as required by the particular ore being processed. Extending downwardly and inwardly from the lower end of each of the baffle plates 38, 38' is a screen 45, 45, respectively, and preferably provided with vibrators (not shown) to facilitate the screening operation.

The spiked mixing rolls 18, 19 as best shown in FIGS. 2 and 3, are each comprised of a metal cylindrical section 50 having removably mounted at spaced points around the outer periphery thereof, a plurality of elongated, generally radially extending spikes or blades 51. The spikes 51 in the preferred form, are triangular in cross section, about 1 to 3 inches wide at the base, with a base flange 52 extending therefrom for removably mounting the same on the cylindrical section 51 and extending outwardly from the surface of the cylindrical section 50 about 2 to 5 inches. The spikes 51 also preferably have a length substantially less than the length of the cylindrical section 50 and are disposed on the outer longitudinal surface thereof in circumferentially spaced and longitudinally or axially staggered relationship (as best seen in FIG. 2) to obtain the optimum mixing of the high moisture content ores with flue dust, or the like, Without permitting buildup of material thereon, as would occur if the spikes extended the full length of the rolls.

In operation, hot blast furnace flue dust is fed from hopper 11 onto the belt 12 of the continuous conveyor means, as the belt travels toward roll 13. As the belt 12 passes below ore hopper 19, wet iron ore is deposited on the surface of the layer of flue dust. The flue dust and iron ore are then discharged from the end of the conveyor means and allowed to fall onto the upper surface of the mixing roll 18 within the mixing zone while the roll 18 is rotatably driven at a relatively high rate of speed by motor 30 through the drive chain 29. The wet ore and flue dust are rapidly accelerated and are thrown by centrifugal force from the surface of the roll 18 and the spikes or blades 51 against the baflle plates 37, 38 which are disposed generally perpendicular to the normal direction of travel of the materials being mixed. Upon striking the baffle plates 37, 38 the forward movement of the ore and flue dust is stopped abruptly and it is during this operation that substantial mixing and drying of the material is effected. The materials are then allowed to fall from the vibrating bafile plates 37, 38 onto a screen of the required mesh size, said screen preferably being continuously vibrated to facilitate the screening operation. The material passing through the screen is found to be a uniform mixture of iron ore and flue dust. If desired, as in the event the mixing roll 18 or an associated part breaks down or does not function properly, the direction of travel of the belt 12 can be reversed and the materials to be mixed can be charged onto the mixing roll 19. An independent drive means is provided for roll 19 as shown in FIG. 1. It is also preferable to reverse the position of the discharge outlets of the hoppers 10, 11 when the direction of travel of belt 12 is reversed so that the wet ore is not deposited directly onto the surface of the belt 12 to which it would tend to stick. By depositing the wet ore onto a layer of dry flue dust, there is no sticking of the ore to the belt 12. The mixing operation can thus proceed without interruption and delay.

It will be understood that the speed at which the mixing roll rotates will depend at least in part on the size of the mixing roll used. Thus, with our particular apparatus the rotational speed of the roll is so adjusted to the diameter of the roll that the material falling thereon is propelled at a high rate of speed against a baifle plate and thoroughly mixed. It will also be apparent that the speed of rotation can be adapted to the particular materials being mixed in accordance with the density, particle size, or other physical properties of the materials or the condition thereof at the time of mixing, in order to obtain the desired mixing. Also, the rate of travel of the belt 12 can be readily adjusted by regulating motor 24 as required by the particular mixing conditions and materials.

The herein described method of mixing wet ore and hot blast furnace flue dust was specifically applied in several runs on material corresponding to the severe conditions frequently encountered at the screen station. The iron ore used was Seine River ore which prior to becoming wet had been screened through a /2 inch screen (minus /2 inch fraction). The wet ore used in the tests closely resembled mud with the moisture content thereof ranging from about 15 to 20%. The hot blast furnace dust was obtained from railroad cars at the sinter plant and was kept hot until the time of the runs. The mixing roll having a diameter of approximately two feet was rotated at a speed of about 250 rpm. The results of the tests are shown in the following Table I:

Table I Moisture Con- Serne River Ore Flue Dust tent of the Mix,

Wt. percent Run No.

Wt. Mois- Wt. Actual percent Temp., ture, percent Temp., Oaleu- (Averm MIX F. Wt. in Mix F. lated age) percent 70 65 15. 30 30 10. 70 10.32 70 60 16. 70 30 200 ll. 70 11. 60 S0 6O 17. 20 20 205 13. 70 12. 33 60 70 17. 20 40 l95 10. 30 9. 87 60 70 19.00 40 200 11.40 10. 92 50 5O 18. 70 50 9. 50 9. 04 50 50 18. 70 50 195 9. 50 9. 17

Visual examinations of the resulting mixtures show that intimate mixing of the wet ore and flue dust was effected in all cases. The test data also show that a sinter feed mixture of comparative uniform moisture content below the theoretical calculated percentage of moisture is produced in each instance.

It is apparent from the foregoing description, that the apparatus and method of mixing of the present invention is well-suited for mixing and drying of iron ore in a'finely divided state, and particularly iron ore which has a high moisture content. It will also be apparent that the present invention is also applicable to the mixing of other materials, such as in preparing cement mixtures, fertilizers, or the like. It should be understood that the term high moisture conten is intended to designate a moisture or liquid content in excess of 12% liquid content by weight and preferably from about 15% to 20%. Also, the term finely divided materials is used in the specification and claims to designate materials having a particle size less than about /2 inch.

Others may practice the invention in any of the numerous ways which are suggested .to one skilled in the art by this disclosure, and all such practices of the invention are considered to be a part hereof which fall within the scope of the appended claims.

We claim:

1. A method of mixing at least two finely divided materials wherein one of said materials has a high moisture content comprising, charging at least two finely divided materials at least one of which has a high-moisture content into a mixing zone, rapidly accelerating said materials in said mixing zone, and abruptly interrupting the movement of said materials while traveling at a high rate of speed by interposing' a baflle member disposed substantially perpendicular to the direction of travel of said materials.

2. A method of mixing at least two finely divided materials comprising, charging a relatively dry finely divided material and a finely divided material having a high moisture content into a mixing zone, said materials being allowed to fall freely into said mixing zone, rapidly accelerating said material in said mixing zone along a pathway extending generally transversely of the path of the freely falling material, and abruptly stopping the movement of said material along the said pathway while traveling at a high rate of speed by interposing a battle member disposed substantially perpendicular to the direction of travel of said materials along said pathway.

3. In a method of continuously mixing and screening at least two finely divided materials where one of said materials has a high moisture content, the improvement comprising; continuously feeding finely divided materials to a mixing zone and allowing said materials to fall freely in said mixing zone, contacting said materials in said mixing zone with means for propelling said materials at a high rate of speed along a pathway generally transversely of the path of said freely falling materials, interrupting the flow of said material being propelled along said pathway to abruptly stop the movement of said material, and directing the said material onto a screening means by interposing a baffle member disposed substantially perpendicular to the direction of travel of said materials along said pathway.

4. In a method of continuously mixing and screening at least two finely divided materials including the steps of depositing'on an endless conveyor means at least two finely divided materials, one of said materials being substantially dry and another of said materials having a moisture content in excess of 12% by weight and below about 20% by weight and comprising between about 50% and 80% of the'total weight of said finely divided materials, and discharging the materials from the said conveyor means into a mixing zone, the improvement which comprises accelerating said materials at a high rate of speed along a pathway generally transversely of the normal movement of said materials through said mixing zone, interrupting the flow of said materials traveling at a high rate of speed by interposing a baflle means disposed substantially perpendicular to the pathway of said materials to abruptly stop the movement of said materials, and directing the said materials onto a screening means.

5. A method of mixing and drying at least two finely divided materials comprising, continuously supplying a freely falling stream of said finely divided materials into a mixing zone comprising a cylindrical means being rapidly rotated about a horizontal axis, one of said finely divided materials being substantially dry and another of said finely divided materials having a moisture content of between about 15% and 20% by weight and comprising between about 50% and 80% of the total weight of said finely divided materials, accelerating said materials to a high rate of speed by contacting with said cylindrical means to propel said materials along a pathway generally transversely of the stream of freely falling material, interrupting the flow of the said material while traveling at a high rate of speed by interposing baflie means disposed rial to abruptly stop the flow of said material, and directing the said materials onto a screening means.

6. In a mixing apparatus, including an endless conveyor means for conveying finely divided materials in a horizontal direction to a mixing means, the improvement comprising; a mixing roll disposed at one end of said endless conveyor means, said mixing roll being rotatable at a high rate of speed and having rigidly secured on the surface thereof a plurality of circumferentially spaced rows of radially extending blades of less transverse length than the length of said roll which are arranged in circumferentially spaced and staggered relationship thereon whereby said roll is adapted to rapidly accelerate said material along a predetermined pathway and baflie plates disposed in spaced relationship from said mixing roll and disposed substantially perpendicular to said pathway for abruptly stopping the movement of material which is propelled thereagainst by said mixing rolls, and means disposed below the said baflie plates adapted to receive material therefrom.

7. In a mixing apparatus having an endless conveyor means for conveying finely divided materials and depositing said material on a mixing roll, the improvement comprising a cylindrical mixing roll having rigidly secured on the outer surface thereof a plurality of circumferentially spaced rows of radially extending blades of less transverse length than the length of said cylindrical mixing roll and said blades being arranged in circumferentially spaced and overlapping staggered relationship on said cylindrical mixing roll and being adapted to engage said finely divided materials deposited on said roll and rapidly accelerate said materials along a predetermined generally transverse pathway.

8. In a method of mixing subdivided solid materials, one of which has a relatively high moisture content to obtain a screenable mixture of reduced moisture content including the steps of separately depositing the materials on a horizontally moving conveyor, the improvement comprising; gravity discharging the materials downwardly from said conveyor onto a high speed rotary device having radially extending propelling surfaces and thereby centrifugally projecting the materials outwardly at high speed, and impinging the outwardly projecting materials against an impact surface interposed in the path of movement of said materials and disposed substantially perpendicular to the direction of travel of said materials along said path.

9. In a method of treating subdivided iron ore material of high moisture content to obtain a screenable prodnet of reduced moisture content suitable for charging to a sintering operation which includes the steps of separately depositing wet iron ore comprising between about 50% and by weight of said product and containing in excess of about 12% by Weight moisture and dry hot flue dust on a horizontally moving conveyor means and mixing the said ore and flue dust, the improvement comprising; discharging the said iron ore and flue dust simultaneously by gravity from the said conveyor means downwardly onto a rotating horizontally disposed mixing roll having radially extending blades moving at high speed, propelling the material centrifugally outwardly by means of said blades, and receiving the propelled material in impinging relation on an impact suface disposed in the path of outward movement of the material substantially perpendicular to said path of movement of said material.

10. The method of claim 9 further characterized in that said wet iron ore contains between about 15 wt. percent and 20 wt. percent moisture.

11. The method of claim 9 further characterized in that said dry flue dust is first deposited on said conveyor means and said wet iron ore is deposited over said flue dust.

l2. Mixing apparatus for mixing wet iron ore with dry flue dust to obtain a product of reduced moisture content suitable for charging to a sintering operation which comprises; a mixing roll disposed in spaced relation below a conveyor for receiving freely falling material from the conveyor, means for rotating said roll at high speed, said mixing roll being disposed on a horizontal axis of rotation and having mounted rigidly thereon a plurality of radially extending blades adapted to engage and rapidly accelerate said iron ore and flue dust deposited on said roll along a path generally transversely of said roll, said blades being shorter than the axial length of said roll and being arranged thereon in circumferentially spaced and axially staggered overlapping relation, and baffle means disposed outwardly of said roll for impingement thereon of material propelled outwardly from said roll by said blades and extending substantially perpendicular to said path along which said material is propelled by said blades.

13. A mixing apparatus as in claim 12, wherein said baflie means has associated therewith means for vibrating said bafile means.

(References on following page) References Cited in the file of this potent UNITED STATES PATENTS Edwards Dec. 10, 1878 West et a1. Oct. 9, 1906 5 De Mier Oct. 18, 1927 Crandell et a1. July 24, 1934 Fulmer Apr. 2, 1935 e3 Wendeborn Aug. 17, 1937 Johnson Sept. 26, 1939 Stewart Dec. 3, 1946 Lyon et a1. July 24, 1951 Edmunds Mar. 18, 1952 Rundle June 10, 1952 Sylvest July 21, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,151,844 October 6, 1964 Michael O. Holowaty et al.

It is hereby certified that error appears in the above numbered patent reqiiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 55, after "disposed" insert substantially perpendicular to the movement of said mate- Signed and sealed this 16th day of March 1965e (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Aitcsting Officer Commissioner of Patents 

1. A METHOD OF MIXING AT LEAST TWO FINELY DIVIDED MATERIALS WHEREIN ONE OF SAID MATERIALS HAS A HIGH MOISTURE CONTENT COMPRISING, CHARGING AT LEAST TWO FINELY DIVIDED MATERIALS AT LEAST ONE OF WHICH HAS A HIGH-MOISTURE CONTENT INTO A MIXING ZONE, RAPIDLY ACCELERATING SAID MATERIALS IN >AID MIXING ZONE, AND ABRUPTLY INTERRUPTING THE MOVEMENT OF SAID MATERIALS WHILE TRAVELING AT A HIGH RATE OF SPEED BY INTERPOSING A BAFFLE MEMBER DISPOSED SUBSTANTIALLY PERPENDICULAR TO THE DIRECTION OF TRAVEL OF SAID MATERIALS. 